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Abstract

The use of functional traits to explain how biodiversity affects ecosystem functioning has attracted intense interest, yet few studies have a priori altered functional diversity, especially in multitrophic communities. Here, we manipulated multivariate functional diversity of estuarine grazers and predators within multiple levels of species richness to test how species richness and functional diversity predicted ecosystem functioning in a multitrophic food web. Community functional diversity was a better predictor than species richness for the majority of ecosystem properties, based on general linear mixed effects models. Combining inferences from 8 traits into a single multivariate index increased prediction accuracy of these models relative to any individual trait. Structural equation modeling revealed that functional diversity of both grazers and predators was important in driving final biomass within trophic levels, with stronger effects observed for predators. We also show that different species drove different ecosystem responses, with evidence for both sampling effects and complementarity. Our study extends experimental investigations of functional trait diversity to a multilevel food web, and demonstrates that functional diversity can be more accurate and effective than species richness in predicting community biomass in a food web context.

Author Comment

This is the final unformatted revision for Ecology.

Additional Information

Competing Interests

The authors declare they have no competing interests.

Author Contributions

Jonathan S Lefcheck conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables.

J. Emmett Duffy conceived and designed the experiments, reviewed drafts of the paper.

Animal Ethics

The following information was supplied relating to ethical approvals (i.e., approving body and any reference numbers):

Vertebrates were handled according to IACUC standards (protocol 2012-05-11-7960 administered through The College of William & Mary).

Funding

JSL was supported by VIMS Council and VIMS Maury Fellowships. JED and JSL were supported by NSF OCE-1031061 to JED. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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